1. Field of the Invention
The present invention relates to an addition curable phosphor-containing adhesive silicone composition, which in an uncured state (namely, prior to heat treatment) at room temperature is either a solid or a semisolid, and which by positioning on, and bonding to, the surface of an LED chip, is capable of converting the blue light or ultraviolet light of the LED. The present invention also relates to a sheet formed of the composition, a sheet-like cured product obtained by heat-curing the sheet, a method of producing a light emitting device that uses the silicone composition sheet, and a light emitting device.
2. Description of the Prior Art
In the field of light emitting diodes (LED), the use of phosphors for wavelength conversion is well known (see patent reference 1). Because silicone resins exhibit excellent light resistance, they are attracting considerable attention as coating materials for encapsulating and protecting LED chips (see patent reference 2).
In white LEDs, a method is generally used in which a silicone resin or epoxy resin with a phosphor dispersed therein is used to coat the LED chip, thereby dispersing the phosphor in a position close to the chip and enabling the blue light from the LED to be converted to a pseudo white light. However, if the dispersion of the phosphor within the resin lacks uniformity or is biased, then color shift becomes more likely, meaning that the phosphor must be dispersed uniformly within the coating resin layer in order to generate a uniform white light. In order to achieve such uniform dispersion, screen printing methods and phosphor precipitation methods are under investigation, but these methods suffer from other problems, including a more complex production process and inadequate stability. Accordingly, a simple technique that enables a phosphor to be dispersed uniformly across a chip surface has been keenly sought.
Furthermore, in LEDs and the like, the resin layer used to coat the LED chip requires high levels of heat resistance and ultraviolet light resistance. Moreover, a resin layer that can be produced using conventional production apparatus would be ideal.
[Patent Reference 1] US 2004/0094757 A1
[Patent Reference 2] US 2004/0214966 A1